Police in the canton of Bern said in a statement on Wednesday they had opened their probe last year when a woman of Thai origin told investigators "she had been held against her will in a Bern establishment and forced to prostitute herself."
Police soon discovered that the network stretched across several Swiss cantons.
The main suspect, a 42-year-old Thai woman with a Swiss residence permit, was arrested during the second half of last year in Germany and had been extradited to Switzerland, Bern police said.
The woman, whose name was not given, appeared to have been actively running the network since the end of 2008.
She operated a brothel where both women and men of Thai origin living in Switzerland illegally worked as prostitutes.
When she was arrested, she was carrying documents including identity papers belonging to the victims, police said.
Most of the victims came from poverty in Thailand.
They had known they would be working as prostitutes in Switzerland, police said, but because of the massive fees the network charged to get them to the country and for being allowed to work in its brothels they effectively became sex slaves.
Each prostitute had to earn at least 60,000 francs ($64,465) and in some cases as much as 90,000 francs ($96,000), before being able to pay down their debt and actually pocket some of the money they made themselves.
In some cases, they had to sign loan contracts offering any real estate holdings they had in Thailand as security, police said.
Most of the victims had returned to Thailand and did not want to press charges or take part in the legal process, law enforcement officials added.
The main suspect has been accused of victimizing 26 people in the canton of Thurgau and 31 others in the cantons of Bern, Solothurn, Lucerne, Basel-City and Zurich.
Six other suspects, a Swiss and a Thai man and four Thai women, are in custody.
Prostitution has been legal in Switzerland since 1992, as long as the sex workers are in the trade of their own free will.